Chinese artist Ai Weiwei throws porcelain sunflower seeds into the air as he poses for a photograph with his new installation entitled 'Sunflower Seeds', at its unveiling in the Turbine Hall at the Tate Modern gallery, in London, October 11, 2010. (� Stefan Wermuth / Reuters/REUTERS)

Chinese artist Ai Weiwei throws porcelain sunflower seeds into the air as he poses for a photograph with his new installation entitled 'Sunflower Seeds', at its unveiling in the Turbine Hall at the Tate Modern gallery, in London, October 11, 2010.(� Stefan Wermuth / Reuters/REUTERS)

Free Ai Weiwei, radical individualist and China's great national artist
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They took down his blog and they smashed his studio, but the Chinese government still couldn't silence Ai Weiwei. On Sunday, as he was preparing to board a flight from Beijing to Hong Kong, police took the world-renowned artist away, and detained several of his assistants. Mr. Ai is by turns a radical individualist and a creator of monuments of great collective meaning. All free people should rally for his immediate release.

Mr. Ai is an agitator and a polymath who has worked in almost every artistic medium. His best-known early work, the photo series "Study of Perspective," features his outstretched hand, "flipping the bird" at various famous monuments - the Eiffel Tower, the White House, Tiananmen Square - in the distance. As his canvasses have grown, so has his ambition. Visitors to the Turbine Hall at the Tate Modern in London can walk through his latest imagining: "Sunflower Seeds": 100 million hand-made, hand-painted porcelain pieces.

He is also, at heart, a patriot: He helped design the Bird's Nest Stadium - a "monument to Beijing's strength and ambition," Mr. Ai called it - the centrepiece of the opening ceremonies of the 2008 Summer Olympic Games.

But he is an inconvenient patriot, the kind who demands better of his country. And so Mr. Ai denounced the stadium before the Games even began, rightly anticipating that the regime would suppress dissent in spite of the Games. His art celebrates, but it also laments, most notably in a memorial mural, made of thousands of children's backpacks, to those killed in the 2008 Sichuan earthquake - victims on whose behalf he continues to campaign.

Why have the Chinese state and the Communist Party tightened the vise around Mr. Ai? Perhaps, as with the recent detention of journalists, it is a defensive measure, in the wake of recent revolutions in the Arab world.

And perhaps it is because Mr. Ai represents freedom. He cherishes it, even videotaping his regular encounters with the police. "When those in power are infatuated with you, you feel valued," he has said.

Tonight, Bob Dylan plays his first ever concert in mainland China. As it welcomes Dylan, China should release Mr. Ai, their own restless artist, who, like the falsely accused in one of Dylan's earlier songs, is now "an innocent man, in a living hell."